The present invention relates to a packet wrapping unit.
The present invention may be used to advantage on cigarette packing machines, in particular cellophaning machines, to which the following description refers purely by way of example.
On cellophaning machines, a packet for overwrapping is generally housed inside a first seat on a first conveyor, normally a conveyor wheel; the first seat is fed to a transfer station in time with a respective second seat on a second conveyor, normally another conveyor wheel; the two seats are aligned for a given length of time; a sheet of wrapping material is supplied to the transfer station and positioned between the two aligned seats; the packet is transferred from the first to the second seat so as to insert the packet inside the second seat together with the respective sheet of wrapping material, which is simultaneously folded into a U about the packet; the packet and respective sheet are released inside the second seat; and two portions of the sheet projecting from the second seat are folded on to the packet and sealed to each other to form a tubular wrapping about the packet.
The above operations for transferring the packets from one conveyor to the other and simultaneously folding the respective sheets of wrapping material into a U present several difficulties, in that correct folding of the sheet of wrapping material into a U about the respective packet normally requires the use of a folding spindle to guide the sheet as it is folded, and, at any rate, at least a sheet guiding device for preventing the sheet from slipping in relation to the packet. Moreover, on account of the thinness of the sheet of wrapping material and the relatively high speed at which the packet is inserted, the sheet, especially when of minimum thickness for ecological reasons, is invariably subject to damage.